We aren’t sure how exactly you diagnose eye problems in an elephant — how big an eye chart do you need? — but C’sar, a 38-year-old elephant at the North Carolina Zoo in Asheboro, N.C. But we do know that the prescription involves contact lenses nearly the size of tennis balls.

Zookeepers started worrying about C’sar after the animal began acting lethargic and losing weight. Veterinarians figured poor eyesight had something to do with the problems, so they ordered cataract surgery. But while the surgery helped, the procedure left C’sar far-sighted. And just because he is an elephant doesn’t mean he can’t wear some contact lenses, the vets figured.

The lenses for the 12,000-pound zoo fixture will stay in for three months at a time.

The first issue for C’sar arose in 2010 when zookeepers noticed some clouding of his eyes, the forming of cataracts, first in his right eye and then in his left. Then C’sar began stubbing his toes regularly and smashing his tusk into things. Eventually he just spent time leaning against a wall in the corner, prompting zookeepers to remove him from exhibition.

Last November, as zoo officials feared they would have to put down the animal, a doctor from North Carolina State University’s College of Veterinary Medicine successfully cleared up his left eye, allowing him to return to the elephant enclosure. In May, they removed the cataract from his right eye. “It was dramatically different, and he seems to be in pretty good shape now,” Dr. Ryan DeVoe, the zoo’s senior veterinarian told the Charlotte Observer. “He’s noticeably brighter, and more interactive and he just moves around differently.”

But curing the cataracts involved removing C’sar’s natural lenses, leaving his vision impaired. So when his eyes heal fully—hopefully this fall—doctors will try out the giant contacts. They aren’t sure if they’ll work, as this is the first time contacts have been used on an elephant to correct vision. The contacts will held in place by the elephant’s third eyelid, which moves vertically across the eye (handy, right?) and they may prove too annoying or get dirty too often. But you can never know until you try it out.

Tim Newcomb is a journalist based in the Pacific Northwest covering sports design and technology, culture, infrastructure and entertainment. He writes for Sports Illustrated, Popular Mechanics, TIME and more.